When cooling is carried out by supporting a cooling surface of a battery module on a hollow cooling plate having a cooling medium flowing through its interior and transferring the heat of the battery module to the cooling plate via the cooling surface, since it is inevitable that a minute gap will occur between the cooling plate and the cooling surface of the battery module, which are both rigid, there is the problem that the performance in cooling the battery module is degraded due to inhibition of thermal conduction between the cooling surface and the cooling plate because of the gap.
In order to solve this problem, an arrangement in which a deformable heat transfer sheet having excellent thermal conductivity is held between a cooling plate and a cooling surface of a battery module and any gap between the cooling plate and the cooling surface of the battery module is eliminated by deformation of the heat transfer sheet to thus promote heat transfer from the cooling surface to the cooling plate, thereby enhancing the performance in cooling the battery module, is known from Patent Document 1 below.